This invention relates generally to an air processing system, and more particularly, to a novel return air control system for use with a heating, cooling and ventilating unit for processing the air in an enclosed area.
Satisfactory processing of the air in an enclosed area requires that the air temperature be kept within a relatively small temperature range. Air processing requirements will, of course, vary with the thermal load in the enclosed area.
Although achieving the desirable control of the air temperature within an enclosed area, presently known air processing systems are inefficient in certain respects. For example, in some of the presently known systems, heat produced by lighting fixtures is virtually ignored. In the heating mode, a majority of the "heat of light" remains substantially localized about the lighting fixture, and it is not used to heat the "lived in" regions of the enclosed area. Thus, primary energy or mechanical heating is required, despite the fact that a substantial quantity of "free heat" is readily available within the enclosed area. This additional primary energy heating significantly increases the operating cost of the presently known air processing systems.
In the cooling mode, the "heat of light" is again ignored. No attempt is made to lessen its adverse effect on room temperature. Additional mechanical cooling is, therefore, required to overcome this "heat of light," which results in relatively high energy use and operating costs.
Additionally, outside air, in certain situations, provides an economical means for cooling an enclosed area. Many of the presently known air processing systems, however, are not properly equipped to use the outside air and instead mechanical cooling is utilized, with an attendant increase in operating costs.
Even in those systems equipped with "outside air cooling means," the inefficiencies, discussed above, limit this operation to periods of time when the outside air temperature is considerably below the desired room temperature. Generally speaking, the presently known systems can be operated in this mode only when the outside air temperature is less than about 56.degree. F.